Electrical apparatus



Aug. 23, 1932. MAURER 1,873,613

ELECTRICAL APPARATUS Filed April 23. 1931 INVENTOR ATTORNEY Patented "Au23, 1932 UNITED STATES PATENT OFFICE PAUL H. MAURER, OF HILLSIDE, NEWJERSEY, ASSIGNOR TO ECLIPSE AVIATION COR- PORATION, OF EAST ORANGE, NEWJERSEY, A CORPORATION OF NEW JERSEY ELECTRICAL APPARATUS Applicationfiled April 23,

The present invention relates to electrical apparatus and moreparticularly to means for preventing sparking across the contacts of acontrol device of the contact type, as for example, a voltage regulator.

In the operation of electrical contacting devices, as for examplecontact voltage regulators, as in the operation of any electricalcircuit-wherein current is interrupted by the making and breaking ofelectrical contacts, considerable sparking takes place across saidcontacts, which in many instances is so great as to cause the fusingtogether-of the contacts, thereby destroying the control device andcausing other hazardous failures of systems in which such controldevices are employed. This is particularly true in installations where acontact voltage regulator is employed with a direct current generator,the shunt field of which has a relatively high inductance and upon themaking and breaking of the regulator contacts this relatively highinductance causes a sudden voltage surge to be induced in the generatorfield winding. The

electromotive-force thus produced by self-induction causes the excessivesparking across the contacts. Accordingly, one of the objects of thepresent invention is to provide novel means whereby excessive sparking,due to the self-induced electromotive-force, is substantially eliminatedand prevented.

Another objeg is to provide in combination with an electric currentgenerator having a voltage regulator of the contact type for controllingthe output thereof, novel means associated with the regulator contactswhereby sparking across said contacts is eliminated and the fusing ofthe latter prevented.

Another object is to provide in combination with an electric currentgenerator having a voltage regulator in which the contacts are adaptedto operate at relatively high speeds for controlling the voltage output.of said generator, novel means associated with the voltage regulatorand the field of the generator, whereby sparkingacross said contacts issubstantially eliminated and fusing thereof prevented. 1

A further object is toprovide in combination with an electricalcontacting device, novel 1931. Serial No. 532,321.

means whereby electrical disturbances in circuits associated with oroperating in the vicinity of said contacting device, due to the sparkingproduced by the operation of the latter, are substantially eliminated orprevented.

Still another object of the invention is to provide in combination withan electric current generator having a field winding of relatively highinductance and a voltage regulator of the contact type wherein thecontacts are adapted to operate at relatively high speeds forcontrolling the voltage output of said generator, novel means embodyingimpedance elements associated with the voltage regulator contacts andthe generator field, whereby sparking across said contacts due to theself-induced electromotive-force produced in the generator field by theoperation of the contacts, is substantially eliminated and wherebydisturbing oscillations which would otherwise be produced by thesparking action, are suppressed at their'source.

The above and other objects and advantages of the invention will be morefully apparent from a consideration of the detailed description whichfollows, taken together with the accompanying drawing wherein isillustrated one embodiment of the invention. It is to be expresslyunderstood, however, that the drawing is for the purpose of illustrationand description only and is not designed as a definition of the limitsof the invention, reference being had for this purpose to the appendedclaims.

The single figure of the drawing is a wiring diagram of one form ofelectrical circuit arrangement embodying the present invention.

The novel means embodying the invention are particularly adapted to beemployed in combination with a direct current generator which isarranged to supply electrical energy to various types of auxliliaryelectrical generator output voltage substantially constant. The voltageregulator is of the type which is illustrated, described, and claimed ina co-pending application of Charles I. McNeil, Serial No. 332,998, filedJanuary 16', 1929 and assigned to the same assignee as the presentapplication.

Referring to the drawing, the armature of the generator to be regulatedis indicated at 1, the field winding which in the present instance is ofa relatively high inductance is indicated at 2, and the field resistanceat 3, said winding and resistance being connected in series acrosspositive and negative output leads 1 and 5 respectively.

The voltage regulator comprises a pair of relatively movable contacts 6and 7 which are normally closed, thereby shunting the resistance 3.Contact 7 is mounted on a vibrating armature 8 which is pivotallymounted in any suitable manner, and adjustable resilient means areprovided, such as a coil spring 9 which is operatively connected to saidannature, to normally maintain contact 7 in engagement with contact 6.

An electro-magnet having a core 10 which is preferably laminated andmade of suitable magnetic material, such as soft iron, is associatedwith armature 8, and spring 9 is so adjusted that when the voltage ofthe generator rises above a predetermined value, the electro-magnet iseffective to overcome the tension of said spring and move contact 7 outof engagement with contact 6, whereupon the field resistance 3 is placedin circuit with the field 2. The resistance of the field circuit is nowof such value as to prevent the desired amount of field current fromflowing, thereby .producing a reduction in the generator voltage. Thisdropping of the voltage weakens the magnetic field of the electro-magnetto such an extent that the contacts 6 and 7 are closed by the spring 9to short-circuit the resistance 3, whereupon the field flux and armaturevoltage will again build up.

The core 10 of the electro-magnet carries a winding 11 which is inseries with a suitable resistance 12, the winding and resistance beingconnected across the output leads a and 5. The magnetic field, set up bycoil 11, rises or falls relatively slowly since it varies in accordancewith the changes in the voltage in the armature. The latter in turnfollows the changes of current in the field. Accordingly 1n voltageregulators embodying only a coil such as is indicated at 11, the openingand closing movements of contacts 6 and 7 are of relatively lowfrequency, i. e., of the order of 10 to 40 cycles per second.

Means are provided for speeding up the action of the contacts wherebythe movement thereof is increased to a relatively high frequency, as forexample, 80 to 300 or more cycles per second. For this purpose the core10 carries a second or auxiliary winding 13 which is connected in serieswith a pair of resistances 14 and 15, and with the contacts 6 and 7being connected across the generator field 2. Coil 13 is wound in such amanner as to strengthen the magnetic field set up in core 10 by the coil11, and the number of ampere turns of both coils are so selected thatthe tension of spring 9 is overcome only when both coils coact toproduce the desired strength of the magnetic field of the core 10.

When the contacts are closed, current flows from the positive outputlead 4 through said contact resistances 15 and 14 and coil 13, thelatter coacting with the coil 11 to set up the magnetic field in core10. When the output voltage of the generator exceeds a predeterminedvalue, as determined by the setting of spring 9, the field of theelectromagnet is sufficiently strong due to the combined action of coils11 and 13 to overcome the tension of spring 9 and move contacts 7 out ofengagement with contact 6. The instant the contacts are opened, thecurrent in coil 13 falls, thus producing a sudden decrease in the fluxof core 10 and this decrease is independent of the fall of the voltagein the armature 1. The regulator armature 8 instantly moves to re-engagecontact 7 with contact 6 due to the action of spring 9. A much quickeraction of the contacts is thus obtained than results from the use of asingle coil such as coil 11, since the magnetic field produced by thelatter falls relatively slowly in accordance with the drop of voltage inthe armature of the generator.

The use of the second or auxiliary coil 13 in combination with the coil11 is sufficient to raise the frequency of the contacts to as high as 80to 300 cycles or more per second. This change in the frequency of thecontacts may not entirel eliminate the intermediate note resulting romthe engagement and disengagement of the contacts, but the note will beof a much higher pitch than that of other sounds resulting from radiowaves which may be transmitted from a signalling system energized by thegenerator, and hence will not interfere with the reception of thesignals at the receiving end.

During the operation of the voltage regulator, a certain amount ofsparking would normally occur at the contacts which would tend to fusethe latter together and thereby destroy the action of the regulator andpossibly produce hazardous failures in the generator supply system. Thisis particularl true when the voltage regulator is employe with agenerator in which thegenerator field has a relatively high inductance,because such high inductance causes a sudden voltage surge to be inducedtherein by self-induction due to collapsing and building up ,of themagnetic field in the generator field winding. The excessive sparkingalso tends to produce electrical oscillations which have a disturbingtems which are highly sensitive to very slight disturbances. It istherefore desirable to suppress these disturbing oscillations andprevent the fusing of the regulator contacts, and to this end novelmeans are provided whereby the excessive sparking across the contacts issubstantially eliminated and prevented. i

In the form shown, the means last referred to comprise an impedancenetwork embodying a pair of parallel circuits including impedanceelements which are constituted by the regulator winding 13, generatorfield w.inding 2, resistances 14 and 15, and a condenser 16 of suitablecapacity. Condenser 16 has one side thereof connected to the junctionpoint between the resistances 14 and 15 and the other side to a leadwhich connects the J coil 13 to the negative output lead 5, and

forms the two parallel circuits mentioned above. One of said parallelcircuits includes the field winding 2, the resistance 15, and thecondenser 16 in series therewith, and the other parallel circuit alsoincludes condenser 16 and resistance 14 and the regulator winding 13 inseries therewith. It will be appar ent from this circuit arrangementthat when the contacts 6 and 7 are open, condenser 16 and the resistance15 are in series with the generator field 2 so that the self-inducedelectromotive-force produced in the field winding 2 by the opening ofthe contacts, will cause the'condenser 16 to become charged, and thecharge which has thus accumulated in the condenser will then bedischarged through the resistance 14 and the winding 13, due to therelative impedance of the field being higher than that of the regulatorwinding, and will be dissipated therein, at' or after which time thecontacts close. It is essential, however, that the values of theresistances 14 and 15, the winding 13 and the condenser 16 be soselected and arranged that the charging of the condenser continues untiltheself-induced electromotive-force collapses at which time thecondenser will discharge through the resistance 14 and the winding 13,thereby dissipating the charge and pre venting sparking across thecontacts 6 and 7.

There is thus provided a novel circuit arrangement whereby sparkingacross the voltage regulator contacts is substantially eliminated andthe radiation of disturbing oscillations, due to such sparking,prevented. The elimination of the sparking also prevents the contactsfrom being fused together and prolongs the life of the contact points.The arrangement is extremely simple and much more eflicient than devicesof the prior art in that the sparking and thedisturbing oscillations aresuppressed without passing through the regulator contacts.

While only one embodiment of the invention has been illustrated anddescribed, changes and modifications which will nowv appear to thoseskilled in the art, maybe made without departing from the scope of theinvention. For example, the auxiliary coil 13 may be eliminated, and theresistance 14 connected to the coil 11 instead, thereby providing avoltage regulator of the conventional type without destroying the effectof the novel spark preventing means of the invention. Reference istherefore to be had to the appended claims for a definition of thelimits of said invention.

What is claimed is:

1. The combination'with a direct current generator having a fieldwinding of relatively high inductance, of a voltage regulator havingrelatively movable contacts and a pair of magnet coils for operating thelatter, a resistance in series" with the field winding and adapted to beshunted by the contacts when the latter are closed, and means associatedwith said fieldwinding and one of said magnet coils for suppressing theelectromotivefor'ce induced in the generator field by the operation ofthe contacts, to prevent sparking across the latter.

2. The combination with an electric generator including a field winding,of a voltage regulator having relatively movable contacts and a pair ofmagnet coils adapted to be energized from said generator for operatingsaid contacts, and means associated with the field winding and one ofthe coils and arranged for storing an electrical charge produced by anelectromotive-force induced in the fieldwinding when the contactsareopen and to dissipate said charge when the in duced electromotive-forcecollapses and be- 106 fore the contacts are closed, to prevent sparkingacross the latter. I

3. In an electrical circuit, the combination of a winding'having arelatively high inductance, an electrical circuit making and break ingdevice having contacts and an actuating winding therefor, a resistanceelement normally in series with said inductance winding and adapted tobe short-circulted hv said device, and means associated with saidinductance Winding and said actuating winding for dissipating theelectrical energy produced in the inductance winding by the operation ofthe contacts. to prevent sparking across the latter. I

4. In an' electrical circuit, the combination of a winding having arelatively high inductance, an electrical circuit making and breakingdevice for controlling the current flow through said winding, aresistance element normally in series with said winding but adapted tobe short-circuited by said device, a pair of magnet windings'arranged tooperate the contacts of said circuit making and breaking. device uponthe occurrence of predetermined conditions in the electrical circuit,and impedance means associated with the inductance winding and one ofthe magnet windings and arranged for storing an electrical chargeproduced by an electromotive-force induced in the inductance windingwhen the contacts are open and to dissipate said charge through saidmagnet winding when the induced electromotive-force collapses and beforethe contacts are closed.

5. In combination, a generator including a field winding, a voltageregulator having relatively movable contacts and an electro-magnet foroperating the latter upon a voltage change in the generator, and meansfor preventing sparking across said contacts due to anelectromotive-force induced in the generator field winding by theoperation of said contacts, said last mentioned means comprising a pairof parallel circuits, one of which includes a condenser, a resistanceand the generator field winding, and the other of which also includessaid condenser and a resistance and the winding of the electro-magnetand the relative impedances of said parallel circuits being such thatthe condenser is charged by the counter electromotive-force induced inthe field winding when the contacts are open, and discharged through thewinding of the electro-magnet when the induced electromotive-forcecollapses and before the contacts are closed.

6. In combination with a generator having a field Winding and a fieldresistance means for regulating the output voltage of said generator byintermittently placing said resistance in circuit with said fieldwinding including a pair of contacts, means including an electro-magnetfor controlling the engagement of said contacts, said electro-magnetembodying a magnet coil in series with said contacts and in parallelwith said winding, and another magnet coil in parallel with saidcontacts, and means associated with one of said magnet coils and saidfield winding for preventing sparking across said contacts due to anelectromotive-force induced in said field winding by the operation ofsaid contacts.

7 In combination with a generator having a field winding and a fieldresistance, means for regulating the voltage output of said generator byintermittently placing said resistance in circuit with said fieldwinding including a pair of coacting contacts, means including anelectro-magnet for controlling the engagement of said contacts, saidelectromagnet embodying a magnet coil in series with said contacts andin parallel with said winding, and another magnet coil in parallel withsaid contacts, and means associated with said field winding and saidseries magnet coil for preventing sparking across said contacts due tothe electrornotive-force induced in said field Winding by the operationof said contacts.

8. In combination with a generator having a field winding of relativelyhigh inductance and afield resistance, means for regulating the outputvoltage of saidgenerator by intermittently placing said resistance incircuit with said field winding including a pair of coacting contacts,means including an electro-magnet for controlling the engagement of saidcontacts, said electro-magnet embodying a magnet coil in series withsaid contacts and in parallel with said fieldwinding, and another magnetcoil in parallel with said contacts, and means for preventing sparkingacross said contacts due to the electromotive force induced in saidfield winding by the operation of said contacts, said last mentionedmeans comprising a pair of parallel circuits, one of which includes acondenser, a resistance and the generator field winding, and the otherof which also includes said condenser, a resistance and the seriesmagnet coil, the relative impedance of the twoparallel circuits beingsuch that the first circuit is adapted to charge said condenser duringthe time that the contacts are open and the second circuit is adapted todischarge said condenser through the magnet coil when the inducedelectromotive-force is collapsed and before the contacts are closed.

9. The combination with an electrical circuit including a winding ofrelatively high inductance and a resistance normally in series with saidwinding of a movable-contact device for intermittently short-circuitingsaid resistance to control the flow of'current through said inductanceWinding, an electromagnet arranged to be energized from said electricalcircuit for controlling the operation of said movable-contact deviceupon the occurrence of predetermined conditions in said circuit, andmeans for preventing sparking across the contacts of saidmovable-contact device due to the electromotive-force induced in saidinductance winding by the op eration of said contact'device, said lastmentioned means comprising a pair of parallel circuits, one of whichincludes a condenser, a resistance and the inductance winding in series,and the other of which also includes said condenser, a resistance andthe winding of the electro-magnet in series, the relative impedance ofsaid parallel circuits being such that the first will be effective whenthe contacts of the contact device are open to cause the inducedelectromotive-force produced in the inductance winding to charge thecondenser, and the second circuit arranged to be effective uponcollapsing of the induced electroniotive-force and before the closing ofthe contacts to dissipate the charge 1 from said condenser through thewinding of therelectro-magnet and the resistance associated therewith.

10. In combination, a winding having relatively high inductance, anelectrical circuit making and breaking device for controlling thecurrent flow through said winding whereby an electromotive-force isinduced therein, said device having actuating windings for operating it,and means associated said inductance winding and one of the actuatingwindings of said, circuit making and breaking device for dissipating theinduced counter electromotive-force so that sparking across the contactsof said circuit making and breaking device is prevented.

11. The combination with a direct current generator having a fieldwinding, of a voltage regulator therefor having relatively movablecontacts and an actuating winding for operating the latter, theoperation of which tends to produce disturbing electrical oscillationsdue to sparking at the contacts caused by an electromotive-force inducedin.

the field winding of the generator, and means associated with the fieldwinding and the actuating winding adapted to accumulate the: chargeproduced by the induced electromotive-force when the contacts are open,and to dissipate said charge upon collapsing of the inducedelectromotive-force and before closing of the contacts to prevent suchsparking across the latter, thereby eliminating the dis turbingelectrical oscillations.

12. The combination with a direct current generator of a voltageregulator therefor having relatively movable contacts,'the operation ofwhich tends to produce disturbing electrical oscillations due tosparking at the contacts caused by an electromotive-foroe induced in thefield winding of the generator, and means adapted to accumulate thecharge produced by the induced electromotive-force when the contacts areopen, and to dissipate said charge upon collapsing of the inducedelectromotive-force and before closing of the contacts to prevent suchsparking across the latter, thereby eliminating the disturbingelectrical oscillations, said last mentioned means comprising animpedance network in cluding the figd winding of the generator, thewinding of the voltage regulator and a pair of resistances in seriestherewith, and a condenser which is connected in parallel with the fieldwinding and the regulator winding.

In testimony whereof I have signed this specification. Y

PAUL H; MAURER.

